1. Field of the Invention
The present invention relates to a fuel injection controller for an in-cylinder injection internal combustion engine that injects fuel directly into a cylinder.
2. Description of Related Art
In recent years, a demand for an in-cylinder injection engine (direct injection engine) having features of low fuel consumption, low exhaust emission and high output has increased rapidly. An in-cylinder injection engine, as described in JP patent No. 3186373, for example, performs a split injection for injecting fuel in split amounts into a cylinder in multiple injection events in an intake stroke during a low rotation period. Thus, even in a state in which an intake flow rate decreases during the low rotation period, an in-cylinder mixture gas, i.e., a mixing state of intake air and injected fuel in a cylinder, can be homogenized through the split injection.
A recent engine has an exhaust gas recirculation device for regulating an external EGR amount (amount of exhaust gas recirculated to an intake system), aiming to reduce emission, for example. If the external EGR amount is increased, the in-cylinder mixture gas tends to become heterogeneous and a combustion state tends to deteriorate. Therefore, a certain engine regulates swirl flow intensity in the cylinder with a swirl control valve to homogenize the in-cylinder mixture gas and to prevent the deterioration of the combustion state. A certain engine having the exhaust gas recirculation device and the swirl control valve reduces an exhaust gas recirculation rate, i.e., the external EGR amount, when the swirl control valve does not operate properly, as described in JP patent No. 2674445, for example.
Aiming at emission reduction and the like, a certain in-cylinder injection engine has an exhaust gas recirculation device for regulating the external EGR amount, a variable valve timing device for regulating an internal EGR amount (amount of combustion gas remaining in the cylinder) by changing a valve overlap amount, a fuel evaporative emission purge device for regulating a fuel evaporative emission purge amount (amount of fuel evaporative emission purged to the intake system) and the like. In this in-cylinder injection engine, if the external EGR amount, the internal EGR amount or the fuel evaporative emission purge amount increases, there is a possibility that the in-cylinder mixture gas becomes heterogeneous and the combustion state deteriorates, worsening drivability.
The technology described in JP patent No. 3186373 performs the split injection during the low rotation period of the in-cylinder injection engine in order to prevent the in-cylinder mixture gas from becoming heterogeneous because of the decrease in the intake flow rate during the low rotation period. However, the technology cannot improve the combustion state when the in-cylinder mixture gas becomes heterogeneous and the combustion state deteriorates due to the increase in the external EGR amount, the internal EGR amount or the fuel evaporative emission purge amount.
The technology described in JP patent No. 2674445 reduces the external EGR amount when the swirl control valve becomes abnormal. However, in the in-cylinder injection engine, the combustion state cannot be improved sufficiently by merely reducing the external EGR amount when the in-cylinder mixture gas becomes heterogeneous and the combustion state deteriorates due to the abnormality of the swirl control valve.